Resonator and fabrication method thereof

ABSTRACT

A resonator fabrication method is provided. A method includes providing a plurality of electrode patterns disposed apart from each other on a substrate using a nano-imprint technique; and forming an extended electrode pattern connected to a plurality of electrode patterns, and forming a nano structure laid across an extended electrode patterns. Therefore, a nano-electromechanical system (NEMS) resonator is easily fabricated at a nanometer level.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of pending U.S. application Ser.No. 12/388,157, filed on Feb. 18, 2009, which claims the benefit under35 U.S.C. §119 from Korean Patent Application No. 10-2008-0039469, filedon Apr. 28, 2008, in the Korean Intellectual Property Office, thedisclosure of which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a resonator and a fabrication methodthereof, and more particularly to a nano-electromechanical system (NEMS)resonator which is fabricated using nanotechnology, and a fabricationmethod thereof.

2. Description of the Related Art

With the advancement of electronic technologies, micro-miniaturizationof various portable devices has become widespread. To fabricatemicro-miniature devices, it is required that the components mountedtherein should also be miniaturized.

Micro-electromechanical system (MEMS) technology, which enables devicesor equipment having a microstructure on a scale of less than a fewmicrometers to be designed, and nano-electromechanical system (NEMS)technology, which enables devices or equipment having anultra-microstructure on a scale of less than a few nano-meters to bedesigned, are increasingly used to develop microminiature and ultralight devices.

NEMS is an electrodynamics system to convert an electronic signal to adynamic motion, and vice versa.

A micro-miniature resonator fabricated using MEMS or NEMS technology maybe used as a component of a filter or duplexer of a portablecommunication device to perform radio frequency (RF) communication.

The size of a resonator, the operating temperature, and the quality (Q)factor are used to determine the performance of a resonator. The Qfactor indicates the quality of frequency selectivity, a higher Q factorenabling a higher performance to be achieved. The larger the resonatorand the lower the temperature are provided, Q factor is higher.

If the resonator embodied with the micro-technology is operated at lowtemperature, a Q factor of more than 10,000 is acquired. However, theresonator should be operated at room temperature, and the resonator isrequired to be small in order to have a bandwidth of GHz. When aconventional resonator fabricated with the micro-technology is used, thebandwidth of the resonator is within a range of hundreds of MHz, and theQ factor is rarely as high.

The resonator has been developed using nanotechnology, but there areproblems, in that it is difficult to handle and dispose ofnano-materials and that the reproducibility is poor.

SUMMARY OF THE INVENTION

Exemplary embodiments of the present invention address at least theabove problems and/or disadvantages and other disadvantages notdescribed above. Also, the present invention is not required to overcomethe disadvantages described above, and an exemplary embodiment of thepresent invention may not overcome any of the problems described above.

The present invention provides a resonator fabrication method to easilyfabricate a resonator using nanotechnology, and also provides aresonator fabricated according to the method.

According to an exemplary aspect of the present invention, there isprovided a resonator fabrication method, including (a) providing aplurality of electrode patterns disposed apart from each other on asubstrate using a nano-imprint technique; and (b) forming an extendedelectrode pattern connected to the plurality of electrode patterns, andforming a nano structure laid across the extended electrode patterns.

Step (a) may include forming the plurality of electrode patternsdisposed apart from each other by forming a photo resist pattern on asurface of the substrate, covering the surface with metal, and removingthe photo resist pattern from the surface; coating a resin layer on theelectrode pattern; and arranging a prepared nano-imprint stamp on thesubstrate, and removing at least one part of the resin layer byperforming the nano-imprint.

Step (b) may include forming the plurality of extended electrodepatterns connected to the plurality of electrode patterns by exposingthe substrate removing the part of the resin layer, and metallizing theexposed substrate; forming a first coating layer connecting theplurality of extended electrode patterns; forming a second coating layerover the whole area excluding the first coating layer; and forming thenano structure laid across the extended electrode patterns by deposing anano material on the first coating layer and the second coating layer,and removing the second coating layer and the nano material on thesecond coating layer.

The operation of forming the first coating layer may include using aphotolithographic technique or a soft lithographic technique.

The first coating layer may be made of a 3-aminopropylitriethoxysilane(3-APS) polymer material, and the second coating layer may be made of anoctadecyltrichlorosilane (OTS) polymer material.

Step (a) may proceed at a micrometer level, and step (b) may proceed ata nanometer level.

The plurality of electrode patterns may be formed at a micrometer level,and the plurality of extended electrode patterns may be formed at ananometer level.

The nano structure may include one of a carbon nano tube, an oxide nanowire, and a polymer nano fiber.

The method may further include fixing the nano structure on theplurality of extended electrode patterns.

The fixing may include additionally coating a resin layer; removing partof the additionally coated resin layer using the nano-imprint technique;and additionally forming a fixed electrode to fix the nano structure tothe plurality of extended electrode patterns by metallizing the partfrom which the resin layer is removed, and removing the additionallycoated resin layer.

According to an exemplary aspect of the present invention, there isprovided a resonator including a plurality of electrode patterns whichare disposed apart from each other on a substrate, and are formed at amicrometer level; and a plurality of extended electrode patterns whichare connected to the plurality of electrode patterns, and are formed ata nanometer lever; and a nano structure which is laid across theplurality of extended electrode patterns, and is disposed apart from asurface of the substrate to resonate.

The resonator may further include a fixed electrode which fixes the nanostructure on the extended electrode pattern.

The nano structure may include one of a carbon nano tube, an oxide nanowire, and a polymer nano fiber.

The resonator may further include an oxide layer and a silicon layerwhich are sequentially disposed between the plurality of electrodepatterns and the surface of the substrate, and provide a space in whichthe nano structure resonates.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or other aspects of the present invention will be moreapparent by describing certain exemplary embodiments of the presentinvention with reference to the accompanying drawings, in which:

FIGS. 1A to 1F are sectional views illustrating the process of formingan electrode pattern in a resonator fabrication method according to anexemplary embodiment of the present invention;

FIGS. 2A to 2E are plan views corresponding to FIGS. 1A to 1F;

FIGS. 3A to 3G are sectional views illustrating the process of producingan extended electrode pattern and a nano structure using a resonatorfabrication method according to an exemplary embodiment of the presentinvention;

FIGS. 4A to 4G are plan views corresponding to FIGS. 3A to 3G;

FIG. 5 is a schematic view illustrating the structure of a resonatorfabricated according to an exemplary embodiment of the presentinvention;

FIGS. 6A to 6C are sectional views illustrating the process of forming afixed electrode in a resonator fabrication method according to anexemplary embodiment of the present invention;

FIGS. 7A to 7C are plan views corresponding to FIGS. 6A to 6C; and

FIGS. 8A and 8B are schematic views illustrating a nano-imprint stampand a soft lithographic stamp.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION

Certain exemplary embodiments of the present invention will now bedescribed in greater detail with reference to the accompanying drawings.

In the following description, the same drawing reference numerals areused for the same elements even in different drawings. The mattersdefined in the description, such as detailed construction and elements,are provided to assist in a comprehensive understanding of theinvention. However, the present invention can be carried out withoutthose specifically defined matters. Also, well-known functions orconstructions are not described in detail since they would obscure theinvention with unnecessary detail.

A resonator fabrication method according to an exemplary embodiment ofthe present invention may include a process of forming a plurality ofelectrode patterns which are disposed apart from each other on asubstrate, and a process of producing an extended electrode patternconnected to the respective electrode patterns and a nano structureinterposed between the extended electrode patterns. The electrodepattern may be fabricated at a micrometer level, and the extendedelectrode pattern and the nano structure may be fabricated at ananometer level.

FIGS. 1A to 1F are sectional views illustrating the process of formingan electrode pattern in a resonator fabrication method according to anexemplary embodiment of the present invention.

Referring to FIG. 1A, a substrate 100 is provided. The substrate may bea silicon-on-insulator (SOI) substrate which is formed by sequentiallylaying a silicon substrate 110, an oxide layer 120, and a silicon film130. A SOI substrate is advantageous, because it has strong adhesionbetween the oxide layer 120 and the silicon film 130, good electricconductibility and thermal conductibility are exhibited on the siliconfilm 130, and the materials of each layer are evenly dispersed over thewhole surface of the layers.

The SOI substrate may be fabricated by disposing an oxide layer and asilicon oxide layer on a conventional silicon substrate in order toreduce fabricating costs.

Referring to FIG. 1B, a photo resist pattern 140 is formed by coating aphoto resist on a substrate, and applying a photolithographic techniqueto the substrate. For example, the photo resist is coated over the wholesurface of the substrate, a position to form an electrode pattern is setusing a photo mask, ultraviolet (UV) lithography is performed to set anarea to etch a photo resist, and etching is executed on the areaexcluding the photo resist pattern 140 as shown in FIG. 1B.

The whole surface of the patterns formed according to the aboveprocesses is metallized, and the photo resist pattern 140 is removedusing lift-off process so as to form the plurality of electrode patterns150 as shown in FIG. 1C. The electrode patterns 150 are spaced apartfrom each other at a predetermined distance on the substrate 100.

While the process of forming the electrode pattern 150 using the photolithographic technique is explained with reference to FIGS. 1B and 1C, asoft lithographic technique may alternatively be used to form theelectrode pattern 150.

Referring to FIG. 1D, a resin layer 160 is coated on the whole surfaceof the substrate 100 on which the electrode patterns 150 are formed.

A space to form the extended electrode pattern using the nano-imprinttechnique is set.

A nano-imprint stamp 300 which is pre-provided and the substrate 100 onwhich the resin layer 160 is coated are arranged as shown in FIG. 1E. Asa nano-imprint stamp 300 is used, the arrangement of the substrate canbe performed conveniently. Accordingly, the position on which theextended electrode pattern is formed may be precisely controlled to thenanometer level. If the arrangement of the nano-imprint stamp 300 andthe substrate 100 are completed, the nano-imprint is performed asindicated by the arrow. The temperature and pressure required when thenanoimprit is performed may be determined according to the type of resinlayer 160.

Part of the resin layer 160 is removed, and an area 165 to form theextended electrode pattern is provided as shown in FIG. 1F.

FIGS. 2A to 2E are plan views corresponding to FIGS. 1A to 1F. If thesubstrate 100 on which the silicon film 130 is coated is provided asshown in FIG. 2A, the photo resist pattern 140 is formed as shown inFIG. 2B.

Referring to FIG. 2C, the plurality of electrode patterns 150 are formedby retaining metal material on the area excluding the photo resistpattern 140.

Referring to FIG. 2D, the resin layer 160 is coated over the wholesurface of the substrate 100, and an area to form the extended electrodepattern using the nano-imprint technique is determined.

The processes illustrated in FIGS. 1A to 1F and 2A to 2E are performedat the micrometer level. Accordingly, the electrode pattern 150 may beformed at a micrometer level, and may be made of gold, silver, orplatinum.

FIGS. 3A to 3G are sectional views illustrating the process of producingan extended electrode pattern and a nano structure using a resonatorfabrication method according to an exemplary embodiment of the presentinvention.

Referring to FIG. 3A, the resin material remaining in the area 165 afterthe nano-imprint is processed is removed by the reactive ion etching(RIE).

After the whole surface of the substrate 100 is metallized, theremaining resin layer 160 is removed by the lift-off processing, so thatthe extended electrode pattern 170 is formed as shown in FIG. 3B. Therespective extended electrode patterns 170 are disposed between theelectrode patterns 150, and spaced apart from each other. The metalprocessing is executed at a nanometer level, and the extended electrodepattern 170 is formed at a nanometer level.

The silicon film 130 and the oxide layer 120 are removed from the areaon which the extended electrode pattern 170 and the electrode pattern150 are not formed as shown in FIG. 3C. The upper silicon film 130 maybe, e.g., removed by performing reactive ion etching (RIE) on thesubstrate 100, and the oxide layer 120 may be, e.g., removed byperforming wet etching.

A first coating layer 175 connecting the extended electrode patterns 170is formed as shown in FIG. 3D. In this case, the soft lithographictechnique may be used. For example, the first coating material may becoated on the soft lithographic stamp, and the first coating materialmay be printed so as to be interposed between the extended electrodepatterns 170.

The photo lithographic technique may also be used to form the firstcoating layer 175. The first coating material may be coated on the areaon which the extended electrode patterns 170 are interposed using thephoto mask and the photo resist. The first coating material may be a3-aminopropylitriethoxysilane (3-APS) polymer material so as to enhancethe performance of attaching the nano structure.

A second coating layer 180 is formed on an area excluding the firstcoating layer 175 as shown in FIG. 3E. The second coating layer 180 isformed using a second coating material which is not mixed with the firstcoating material. Specifically, the second coating material may be anoctadecyltrichlorosilane (OTS) polymer material. Thus, the secondcoating layer 180 may be formed on an area excluding the first coatinglayer 175.

A nano material is deposited as shown in FIG. 3F. The nano material isdeposited on the first and second coating layers 175 and 180. The nanomaterial coated on the first coating layer 175 forms a nano structure190.

Specifically, the nano structure 190 can be, for example, a carbon nanotube, an oxide nano wire, or a polymer nano fiber.

As described above, since the first coating layer 175 is a highlycementitious material and adheres well with the nano material, the nanostructure 190 may be connected in a fixed manner between the extendedelectrode patterns 170.

The second coating layer 180 is removed as shown in FIG. 3G. In thiscase, the nano material coated on the second coating layer 180 is alsoremoved, and then, the first coating layer 175 not having the nanostructure 190 is removed by dry etching. As a result, a resonatorstructure is fabricated as shown in FIG. 3G.

Even when a nano structure is fabricated in a bridge shape and operatesat room temperature, a high Q value is acquired. As the Q value of ageneral silicon carbide (SiC) resonator is in inverse proportion to anincrease in temperature, it is difficult to acquire a high Q value atroom temperature. The resonators operate within the MHz band in order tomaintain a high Q value. As described in an exemplary embodiment of thepresent invention, if a nano structure such as a carbon nano tube isused, the resonator may operate at a band of over 10 GHz even at roomtemperature.

FIGS. 4A to 4G are plan views corresponding to FIGS. 3A to 3G.

Referring to FIG. 4A, part of the area 165 is removed while the resinlayer 160 is coated on the whole surface of the substrate 100, and thusthe silicon film 130 and the electrode pattern 150 are exposed.

Referring to FIG. 4B, the resin layer 160 is removed after the wholesurface is metallized, and the extended electrode pattern 170 connectedto the electrode pattern 150 is formed. The width of the extendedelectrode pattern 170 may be less than that of the electrode pattern150.

Referring to FIG. 4C, the silicon substrate 110 is exposed so that thesilicon film 130 and the oxide layer 120 on the area excluding theextended electro pattern 170 and the electrode pattern 150 may beremoved.

Referring to FIG. 4D, the first coating layer 175 is interposed betweenthe extended electrode patterns 170.

The second coating layer 180 is formed over the whole surface of thesubstrate 100 as shown in FIG. 4E. The second coating layer 180 is madeof a material incompatible with the first coating layer 175, so that thesecond coating layer 180 is formed on an area excluding the firstcoating layer.

Referring to FIG. 4F, if nano materials are disposed, part of the nanomaterials are covered on the first coating layer 175, and thus the nanostructure 190 is formed.

If the first and second coating layers 175 and 180 are removed, the nanomaterials coated on the second coating layer 180 are also removed.Accordingly, the nano resonator is fabricated as shown in FIG. 4G.

As described above, both micro processing and nano processing are usedto fabricate the resonator, so the advantage of each may be maximized.Specifically, the resonant region is provided at a nanometer level, andthe resonator is used within the GHz band, and the resonant region isalso provided at a micrometer level. Therefore, the resonator is easilyconnected to an external electrode.

In the resonator fabrication method according to an exemplary embodimentof the present invention, high-cost nano processing is applied to partof the substrate. Therefore, economic efficiency is enhanced.

FIG. 5 is a schematic view illustrating the structure of a resonatorfabricated according to an exemplary embodiment of the presentinvention. Referring to FIG. 5, while three resonators are provided, thenumber of resonators may be adjusted according to the fabricator'sintended application.

The respective nano resonators may include the electrode patterns 150,the extended electrode patterns 170, and the nano structure 190interposed between the extended electrode patterns 170. In FIG. 5, theresonator placed at the center of the silicon substrate 110 includes theelectrode pattern 150 and the extended electrode pattern 170 of the samewidth, whereas the width of the extended electrode pattern 170 may benarrower than that of the electrode pattern 150 as shown in FIG. 4G.

The resonators placed on both sides include the electrode patterns 150formed in a different shape from that of the resonator placed at thecenter. The electrode pattern 150 may be formed in various shapes to beeasily connected to external electrode circuits.

The first coating layer 175 positioned between the nano structure 190and the extended electrode pattern 170 may be made ofaminopropylitriethoxysilane (APS) polymer material which adheres well tothe nano structure 190 as described above. There is an opportunity toimprove adhesion between the nano structure 190 and the extendedelectrode pattern 170.

According to an exemplary embodiment of the present invention, a resinlayer 210 is additionally coated over the whole surface of the resonatoras shown in FIG. 6A.

Part of the resin layer 210 is removed so that the extended electrodepattern 170 connected to the nano structure 190 is exposed as shown inFIG. 6B. Part of the electrode pattern 150, part of the extendedelectrode pattern 170, and part of the nano structure 190 are exposed onthe area 220 from which the resin layer is removed. The resin layer 210may be removed using the nano-imprint technique.

The resin layer 210 is removed after the whole surface, is furnishedwith metal, so the metal remains on the area 220 from which the resinlayer 210 has been removed. The metal remaining on the area 220 fromwhich the resin layer 210 has been is used as a fixed electrode 230 tofix the nano structure to the extended electrode pattern 170. As aresult, the fixed electrode 230 causes the nano structure to be stablyfixed to the extended electrode pattern 170.

FIGS. 7A to 7C are plan views corresponding to FIGS. 6A to 6C.

The resin layer 210 is coated over the whole surface as shown in FIGS.6A and 7A, and part of the resin layer 210 is removed as shown in FIGS.6B and 7B. The width of the area 220 from which the resin layer 210 hasbeen removed may be identical to that of the extended electrode pattern170. The whole surface is covered with metal, and the resin layer 210 isremoved. Thus, the fixed electrode 230 is formed.

The resonator including the fixed electrode 230 may be fabricated asshown in FIGS. 6C and 7C.

FIG. 8A is a schematic view illustrating a nano-imprint stamp used whenfabricating a resonator according to various exemplary embodiments ofthe present invention. If a nano-imprint stamp 300 having uniform sizeis used, the nanoinprint stamp 300 is easily arranged on the substrate100. The position of the extended electrode pattern 170 may be preciselyadjusted at the nano level.

FIG. 8B is a schematic view illustrating a soft lithographic stamp 400used when forming the first coating layer 175. The length of thestamping area of the soft lithographic stamp 400 may be longer than theinterval between the extended electrode patterns 170. Accordingly, thefirst coating layer 175 may be interposed between the extended electrodepatterns 170 by stamping the soft lithographic stamp 400.

As described above, the nano structure 190 can be, for example, a carbonnano tube, an oxide nano wire, or a polymer nano fiber.

The foregoing exemplary embodiments and advantages are merely exemplaryand are not to be construed as limiting the present invention. Thepresent teaching can be readily applied to other types of apparatuses.Also, the description of the exemplary embodiments of the presentinvention is intended to be illustrative, and not to limit the scope ofthe claims, and many alternatives, modifications, and variations will beapparent to those skilled in the art.

What is claimed is:
 1. A resonator, comprising: a plurality of electrodepatterns which are disposed apart from each other on a substrate, andare formed at a micrometer level; and a plurality of extended electrodepatterns which are connected to the plurality of electrode patterns, andare formed at a nanometer lever; and a nano structure which is laidacross the plurality of extended electrode patterns, and is disposedapart from a surface of the substrate to resonate.
 2. The resonator ofclaim 1, further comprising: a fixed electrode which fixes the nanostructure on the extended electrode pattern.
 3. The resonator of claim1, wherein the nano structure comprises one of a carbon nano tube, anoxide nano wire, and a polymer nano fiber.
 4. The resonator of claim 1,further comprising: an oxide layer and a silicon layer which aresequentially disposed between the plurality of electrode patterns andthe surface of the substrate, and provide a space in which the nanostructure resonates.
 5. The resonator of claim 1, wherein the resonatoris capable of operating at a band of over 10 gigahertz (GHz) at atemperatures of approximately 72 degrees.